1. Field of the Invention
The present invention relates to a process cartridge detachably mountable to a main body of an electrophotographic image forming apparatus, a space securing member between a photosensitive drum and a developing roller, a charging roller or the like, a developing device and a charging device.
In the present specification, the electrophotographic image forming apparatus forms an image on a recording medium with using an electrophotographic image forming process. The electrophotographic image forming apparatus may be exemplified by, for example, an electrophotographic copying machine, an electrophotographic printer (for example, a laser beam printer, an LED printer or the like), a facsimile machine, a word processor and so on.
Also, the process cartridge makes charging means, developing means or cleaning means and an electrophotographic photosensitive drum integrally into a cartridge which is detachably mountable to the main body of the electrophotographic image forming apparatus. The process cartridge also makes at least one of the charging means, the developing means and the cleaning means and an electrophotographic photosensitive drum integrally into a cartridge which is detachably mountable to the main body of the electrophotographic image forming apparatus. The process cartridge further makes at least the developing means and the electrophotographic photosensitive drum integrally into a cartridge which is detachably mountable to the main body of the electrophotographic image forming apparatus.
2. Related Background Art
An image forming apparatus such as a printer using an electrophotographic process conducts image recording in such a manner that a photosensitive drum which constitutes an image bearing member is uniformly charged, the photosensitive drum is selectively exposed to form a latent image, the latent image is visualized by toner, which is a developer, the toner image is transferred onto a recording medium, and heat or pressure is applied to the transferred toner image, to thereby fix the toner image onto the recording medium.
The image forming apparatus thus structured may be accompanied by the supply of toner and the maintenance of various process means, and in such image forming apparatus the photosensitive drum, the charging means, the developing means, the cleaning means and so on are gathered within a frame and made into a cartridge as means for facilitating the supply of toner and the maintenance of the apparatus.
In the apparatus of the above type, the space between the photosensitive drum and a developing sleeve that supplies toner to the photosensitive drum must be maintained at a predetermined distance. As this method, a space securing member called an xe2x80x9cSD runnerxe2x80x9d is disposed on an end portion of the developing sleeve, and the gap (hereinafter referred to as the xe2x80x9cSD gapxe2x80x9d) between the photosensitive drum and the developing sleeve is managed by the thickness of the SD runner. Also, the photosensitive drum and the developing sleeve rotate mutually forward in such a manner that the peripheral surfaces of the photosensitive drum and the developing sleeve move in the same direction at the opposite portions of those members, and the SD runner holds the SD gap while rotating in that direction. In this system, the SD runner is urged by an urging force (hereinafter referred to as the xe2x80x9cSD pressurexe2x80x9d) of a spring or the like so as not to separate an abutting portion of the SD runner from the photosensitive drum due to vibration or the like.
In a system using the SD runner, in the case where the rotating direction of the photosensitive drum and the rotating direction of the developing sleeve are in the forward direction, the SD gap can be maintained without any problem. However, in the case where the rotating direction of the photosensitive drum is counter to the rotating direction of the developing sleeve, the peripheral speed difference between the photosensitive drum and the developing sleeve becomes larger than that in the case where the photosensitive drum and the developing sleeve rotate in the forward direction. As a result, there is a fear that the SD runner may be worn away.
Also, in recent years, in a charging device that uniformly charges the photosensitive drum, there is a structure in which the SD gap between the photosensitive drum and the charging roller needs to be held constant. However, in this structure, the rotating directions of the photosensitive drum and the charging roller are also counter to each other.
An object of the present invention is to provide a space securing member which is capable of maintaining the space between rotary members with high accuracy, a developing device using the space securing member, a charging device using the space securing member and a process cartridge using the space securing member.
Another object of the present invention is to provide a space securing member which is capable of maintaining a space between an electrophotographic photosensitive drum and a developing roller with high accuracy, a developing device using the space securing member and a process cartridge using the developing device.
Still another object of the present invention is to provide a space securing member which is capable of maintaining a space between an electrophotographic photosensitive drum and a charging roller with high accuracy, a charging device using the space securing member and a process cartridge using the charging device.
Yet still another object of the present invention is to provide a space securing member having a circular hole rotatably supported by a rotary member and an arc configuration which is in area contact with an outer peripheral surface of another rotary member, a developing device using the space securing member, a charging device using the space securing member and a process cartridge using the space securing member.
These and other objects, features and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.